A tie that appeared awkward for the Premier League club when the draw was made posed no problems for a Sunderland side playing with the sort of confidence and conviction that was so badly lacking under Steve Bruce. The statistics say it all: O'Neill has overseen five victories in his seven matches in charge; Bruce managed two in 14 games this season and within that sequence was a chastening Carling Cup exit at Brighton.

Championship opposition was much more easily overcome here as second-half goals from the impressive Sebastian Larsson and the lively James McClean extinguished Peterborough's hopes of causing an upset.

There was more than a touch of good fortune about Larsson's free-kick, which was an intended cross that crept inside the far post, but Sunderland thoroughly deserved a lead that was doubled moments later when McClean, who had earlier struck the woodwork, registered his second goal in six days with a well-taken header.

Although Peterborough came into this game on the back of a five-match unbeaten run, Darren Ferguson's side looked nervous from the outset, inviting Sunderland to seize the initiative. In the opening seven minutes, Larsson shot across the face of the goal after escaping on the right flank and Craig Gardner picked George Boyd's pocket before stinging Joe Lewis's hands with a 30-yard drive. Moments later Gardner again caused consternation in the Peterborough defence, this time with a whipped centre from the right that Ryan Bennett could easily have turned into his own net.

Tommy Rowe stabbed a shot narrowly wide and Paul Taylor broke from deep before curling a left-footed effort that drifted beyond the far post but those were rare Peterborough attacks in a first half when Sunderland were largely in control. Phil Bardsley and Larsson linked particularly well on the right flank and it was a move involving those two that culminated in McClean hammering a left-footed shot from the edge of the penalty area against the crossbar. Larsson also provided the cross that led to Lewis repelling a close‑range Gardner header 10 minutes before the interval.

Peterborough's resistance was finally broken in the 48th minute, albeit in fortuitous circumstances as Larsson's free-kick from wide on the left eluded everyone – Gardner came close to getting a touch and might have been able to claim the goal if his hair was an inch longer – and found the far corner. The game was effectively over 10 minutes later when McClean met Larsson's free-kick with a glancing header that left Lewis stranded.